Certain forms of incontinence in women have been linked to poor muscle tone in the pubococcygeus or pelvic floor muscles. The muscles extend from the pubic bone to the coccyx; they interdigitate with the sphincter muscles that encircle the anal canal and the urethra and they surround and underlie the vagina. Exercises of the pelvic floor muscles have been evaluated and shown to be effective in improving muscle tone and eliminating incontinence. During childbirth the pelvic floor muscles and their nerve supply are subject to considerable stress. Exercise of the pelvic floor muscles is also considered desirable in preparing for childbirth and recovery therefrom.
Although pelvic floor muscles are striated and innervated by the somatic nervous system, voluntary control of them is often limited. Following trauma to the muscles themselves, or their innervation, such control may be even less available.
One device for providing exercise to the pelvic floor muscles is described in U.S. Pat. No. 4,895,363 to Plevnik et al. and entitled "Set of Parts and Methods for Testing and/or Strengthening Pelvic Floor Muscles." According to the method of this patent, one of a set of weights "cones" is inserted into the vagina and held in place for a period of time. The weight of the cone against the pelvic floor muscles provides a sensation that the cone is slipping out which in turn causes the pelvic floor muscles to contract and also sensitizes the user to this contraction so as to be able to assist in voluntary control of the contraction. Different cones of different weights are used as a means of graduated muscle training and as a means of evaluating muscle tone.
As noted by Plevnik, the contraction of the pelvic floor muscles in holding the cones in place may be accompanied by an unconscious contraction of the abdominal muscles which creates a pressure, forcing the cone out. It is believed that the failure of some patients to benefit from exercises using the Plevnik cone, in treating their stress incontinence, may result from their continued habit of contracting their abdominal muscles along with their pelvic floor muscles. Thus interaction of the abdominal muscles and the pelvic floor muscles also complicates the use of the Plevnik devices in evaluating muscle tone.